2011 is the International Year of Chemistry, reflecting the crucial importance of the physical sciences. To drive this point home and to demonstrate their power, the International Union of Pure and Applied Chemistry has decided to update the atomic weights of 11 elements, as described in this Ars Technica article and directly on the IUPAC site. The changes are relatively small, and elements with several common isotopes are now expressed as a range reflecting common ratios found in nature. For your convenience I've reproduced the updated atomic weights here.

Note that both Hydrogen and Oxygen have been updated. As water (H2O) is the largest component of the human body by mass, you may notice a difference on the scale in the morning. The good news is that in both Hydrogen and Oxygen the lower end of the new range is lighter than the old value, so on some days you may find that you weigh less than before. Unfortunately it is more likely to find yourself made up of heavier variants of the molecule. If this happens, try switching to a different brand of bottled water or moving to an area with a different source of municipal water.

A more significant adjustment is in the atomic properties of Silicon, which forms the basis of nearly all electronic technology. It is impossible to predict the full ramifications of this move, however it is hoped that they will be relatively minor. GPU results are likely to be slightly red-shifted, and you may need to adjust your monitor to compensate. There is absolutely no truth to the rumor that the change in Silicon will make it impossible for hackers to attack systems, please continue with your current vigilance and don't slack off on anti-virus and firewall software. Note that Germanium is also being adjusted, so a quick switch to a different semiconductor wouldn't help.

The most important take-away message is: Don't Panic. Sure, the Sun is mostly Hydrogen and we're blithely mucking with it, but there has been absolutely no credible evidence published in peer reviewed scientific journals that this will lead to a supernova, nor is there time to make it through the peer review process before the alleged supernova would happen. Don't believe anything you may read on the Internet making claims to the contrary.